Items 90-93

There are common features to many intercellular adhesions. These include involvement of cytoskeletal elements, transmembreane linker glcoproteins, and intracellular attachment proteins. Match the type of intercellular adhesive junction in the answers below with the ONE best description in the items below.

( A ) Zonula adherens
( B ) Focal adherension plaque
( C ) Macula adherens
( D ) Hemidesmosome

90. The tranamembrane linker glycoprotein here is integrin.

91. The crucial cytoskeletal element here is the microfilament and casherins are the transmembrane linker glycoproteins.

92. The crucial cytoskeletal element here is the intermediate filament and the intracellular attachment protein is plakoglobin.

93. The transmembrane linker glycoprotein is a cruciform molecule.

ANSWERS AND TUTORIAL ON ITEMS 90-93

The answers are: 90-B;91-A;92-C;93-D. The zonula adherens ( A ) is an apical cell-cell adhesive junction between many epithelial cells. It is supported by microfilaments. Homophilic interactions between cadherins join cells together at these adhesive junctions. Catenins link microfilaments to the cytoplasmic domain of caherins. The focal adhesion plaque ( B ) is a cell-matrix adhesion site. Cells adhere to extracellular glycoiproteins such as fibronectin via ? 5 ? 1 heterodimeric integrin, the fibronectin receptor. Microfilaments support this adhesion mechanism. These cytoskeletal elements are connected to integrin via the intracellular attachment proteins vinculin, talin, and ?-actinin.

The macula adherens ( desmosome ) ( C ) is a strong intercellular adhesions. It uses desmocollins and desmogleins as the transmembrane linker glycoproteins, intermediate ( keratin ) filament as the cytoskeletal support elements, and plakoglobin and desmoplakins as the intracellular attachment proteins. The hemidesmosome ( D ) binds epithelial cells to the basement membrane underlying the epithelium. One of the major constituents of this basement membrane is the cruciform extecellular matrix glycoprotein laminin. A different kind of integrin heterodimer ( ? 6 ? 1 ) is the laminin receptor. The cytoskeletal elements involved in hemidesmosomes are intermediate filaments. Projection Microscopes Student High Power Microscopes Student Low Power Microscopes